The present invention relates to construction of an offshore facility generally known as a retained island. More particularly, the present invention relates to the construction of a retained island suitable for drilling and/or production of minerals such as gas and/or liquid hydrocarbons.
Construction of retained islands to provide an offshore facility for the drilling and/or production of hydrocarbons is known. In the construction of such islands, a berm may be formed to raise the ocean floor to a predetermined level below the mean water level. The berm may be formed of any known land fill and generally has a flat plateau surface with downwardly and outwardly extending sloped surfaces from the plateau area to the ocean floor. One known method of completing the offshore facility is to float a barge to the berm and jacking or skidding the barge up onto the plateau surface of the berm. Thereafter, offshore drilling rigs and production equipment are installed on the barge. Thus, the prior art contemplates fabrication of the retained island and installation of facilities and equipment at the offshore location. Such offshore fabrication and installation is quite expensive due to the need for transportation of components to the site and the fabrication being conducted offshore and often in an hostile environment such as the Harrison Bay area of the Arctic Ocean off the north coast of Alaska.